Pneumatic liquid dispensers are known as mechanisms for discharging, or performing dropwise addition of, a liquid onto a substrate surface or the like. In liquid dispensers, a pump or other pressurizing element is used to pressurize a liquid, and the liquid is added dropwise or discharged from a nozzle of a prescribed diameter and applied to a target substrate surface or the like. Patent Documents 1-3 describe such liquid dispensers.
Additionally, it is difficult to form fine patterns in semiconductor manufacturing steps and the like by using pneumatic liquid dispensers, and thus electrostatic-discharge-scheme liquid discharge heads or the like are used in such applications. The inventors proposed such a liquid discharge head in Patent Document 4.
A micro-flow meter for metering and dispensing liquids was proposed in Patent Document 5. The proposed micro-flow meter comprises a flexible tube of fixed inner diameter through which a liquid is supplied from a liquid container, the micro-flow meter being configured such that the flexible tube is compressed by a pushing device driven by a piezoelectric actuator, and a microvolume of a liquid is discharged from an outlet hole formed in one end of the flexible tube.
Variations in volume due to the fast movement of the pushing device create a flow of liquid toward the outlet hole of the flexible tube, while creating a backflow of liquid through an inlet passage to the liquid container. Additionally, the pushing device is positioned close to the outlet hole, and in portions where the flexible tube is pushed by the pushing device, the liquid impedance on the outlet-hole side is lower than the liquid impedance on the upstream inlet-passage side, causing the majority of the pushed-out liquid to be discharged from the outlet hole. Furthermore, the surface of the flexible tube pushed by the pushing device is formed into an inclined surface set back toward the outlet-hole side; when the flexible tube is pressed by a pressing device, a large amount of liquid is pushed out toward the outlet side. Specifically, in order to determine the discharge amount according to the pipeline-resistance ratio and quickly discharge the liquid from the outlet hole, the flexible tube is deformed so as to assume an axially asymmetrical state.